Antonyms for the phrase "standing to reason" include the words illogical, unreasonable, irrational, and baseless. When something does not "stand to reason," it means that it lacks logical evidence or reasoning to support its validity. An argument may be considered illogical if it contains fallacies or contradicting statements. Similarly, if an assertion is made without any logical or factual basis, it may be deemed baseless. An unreasonable or irrational argument is one that is not based on clear or objective reasoning. Therefore, it is important to ensure that any claims made are supported by reliable and logical evidence to avoid being labeled as illogical, unreasonable, irrational, or baseless.